Not Applicable.
Not Applicable.
The invention relates to earth retaining walls constructed from precast concrete blocks, and more particularly to a connection for securing a geogrid fabric to an earth retaining wall constructed from stacked concrete blocks.
Earth retaining walls are frequently constructed from stacked precast concrete blocks. After the blocks are stacked on a suitable foundation, the earth side of the wall is filled with backfill. The maximum height of the retaining is limited by a number of factors, including the size and weight of the blocks, the foundation for the wall, the type of backfill and surrounding earth, and drainage. It is well known that a higher retaining wall can be constructed if the wall is secured to the adjacent earth with a geogrid system.
Various types of systems have been used in the past for stabilizing concrete block earth retaining walls. In one type of system, ground anchors are embedded in the earth behind the retaining wall and are connected through cables or rods to the wall to prevent the wall from moving. In another type of geogrid system, a perforated geogrid fabric is buried in the earth behind the wall. After one or more tiers of blocks are stacked to form a portion of the wall, backfill is added behind the wall to substantially the level of the top of the stack. The fabric is laid over the backfill and over the top of the adjacent blocks. The next tier of blocks are then stacked on the wall on top of the fabric. Different types of fabric have been used in geogrid systems of this type, including metal fabrics and fabrics formed from a tough, stable synthetic resinous material. The fabric is formed with sufficient openings or perforations to allow water to freely pass through the fabric, and to help the fabric to grip the adjacent soil.
U.S. Pat. No. 6,416,257 shows a geogrid system in which a groove is formed across the top of each block to extend parallel to the face of the block. The bottoms of the blocks forming an adjacent upper tier include a projection which extends part way into the groove. A geogrid fabric is laid over the top of the blocks in a tier and an elongated flat member is inserted into the groove, forcing the fabric into the groove. When a block is positioned in an adjacent upper tier, the bottom projection pushes the elongated member in the groove to secure the geogrid fabric to the block. With this system, it may be possible for a strong force to pull the fabric from between the tiers of blocks.
U.S. Pat. No. 6,019,550 teaches a method for securing a perforated plastic fabric to concrete block earth retaining wall. The blocks are formed with vertical passages which are aligned when the blocks are stacked. Pins are inserted in the passages to prevent the blocks from shifting relative to each other in a horizontal plane. A groove is formed in the top of each block to extend parallel to the face of the block. After a tier of blocks is stacked and backfill is added behind the wall, a geogrid fabric is placed to extend over the top of the blocks and the backfill. A special anchor member is then placed in the groove on top of the fabric. The anchor member includes longitudinally spaced projections which extend through the perforations in the fabric. When the next tier of blocks is stacked on the wall, the anchor member is confined in the groove and secures the fabric to the wall. The anchor member is designed for use with blocks having a top groove sized to receive the anchor member and the fabric and having projections which have the same longitudinal spacing as the spacing between perforations in the fabric. Also, it is necessary to align the fabric with the wall blocks so that a row of perforations are positioned to receive the anchor member when the anchor member is inserted into the groove in the top of the blocks.
The invention is directed to a connection for securing a geogrid fabric to a concrete block earth retaining wall for stabilizing the wall. According to the invention, a groove is formed in the top of each block to extend across the width of the block substantially parallel to the face of the block. The groove in each block will connect with the grooves in the tops of any adjacent blocks in a tier. After blocks in a tier are positioned for constructing a wall, the area behind the wall is backfilled and the geogrid fabric is laid over the backfill and the top of the blocks so that an end of the fabric extends past the groove formed along the top of the tier. A first steel rod is then positioned on top of the fabric and pressed into the groove. If the grooves are longer than first rods, two or more rods are positioned end to end to extend the length of the groove. The end of the fabric is folded over the rod to extend towards the back of the wall. One or more second rods are then placed in the groove above the fabric to the rear of the first rods. The next tier of blocks is then positioned on top of the previously constructed tier of blocks and the geogrid fabric. This tier of blocks closes the groove on the top of the adjacent lower tier and confines the rods to the groove. If a force attempts to move the regaining wall, pulling on the geogrid fabric, the first and second rods become wedged in the groove to prevent slippage of the fabric. Accordingly, a simple construction is provided for securing a geogrid fabric to stacked blocks which form a retaining wall.